Pope Francis told newly ordained bishops yesterday that they must reject all forms of abuse and work in communion to fight the clerical culture that has fuelled the sex abuse and cover-up scandal rocking his papacy.

Francis cited his recent letter about combating abuse during an audience with 74 new bishops from 34 developing countries. The bishops were in Rome for training this week.

Their seminar took place during a crisis for the pope: a lone archbishop has alleged Francis covered up for a now-former US cardinal who was accused of sexually molesting children and adult seminarians.

Francis has ignored calls from clergy and ordinary faithful to respond directly to the claims, saying there were times when "silence and prayer" were the best response.

However, the pontiff spoke in a general way about the Catholic Church's abuse scandal to the new bishops. Many of them hail from dioceses where mishandled clerical abuse cases haven't erupted publicly like it has in the United States, Europe and parts of Latin America.

"Just say no to abuse - of power, conscience or any type," Francis said, adding that to do so the bishops must reject the clerical culture that often places clergy on a pedestal and which Francis himself has blamed for feeling the scandal.

Francis also told the new bishops they are there to serve their flocks, and must work in communion with the church, not as lone actors.

"The bishop can't have all the gifts - the complete set of charisms - even though some think they do, poor things," Francis said. The church, he said, needs unity of bishops "not lone actors working outside the chorus, conducting their own personal battles".

It was perhaps an indirect swipe at Archbishop Carlo Maria Vigano, who broke with centuries of Vatican protocol and pontifical secret to name names and denounce two decades of cover-up by top Vatican bishops, cardinals and popes of the misconduct by ex-Cardinal Theodore McCarrick.

REHABILITATION & SANCTIONS

Specifically, Vigano said he told Francis about McCarrick in 2013, but claimed Francis nevertheless rehabilitated the American cardinal from sanctions that Pope Benedict XVI purportedly imposed in 2009 or 2010.

The Vatican has refused repeated requests for information about what, if any, sanctions were imposed on McCarrick, and what, if anything, Francis did about them.

Vigano's bombshell accusations have plunged the papacy into crisis, with a steady trickle of revelations coming out about who knew what and when about McCarrick - and what they did with that information.

On Friday, Catholic News Service, the news agency of the US bishops' conference, published a 2006 letter from a top Vatican official confirming that the Holy See knew as early as 2000 about McCarrick's penchant for inviting seminarians into his bed.

The letter, from now-Cardinal Leonardo Sandri, confirmed a key part of Vigano's testimony: That a New York City priest, the Reverend Boniface Ramsay, had written the Vatican's US ambassador in November 2000 complaining about McCarrick's behaviour.

Previously, there were reports that a group of concerned Americans had travelled to the Vatican in 2000 to complain about McCarrick, and Ramsay himself had said he had written the letter in 2000.